Still image capturing devices are used to visually memorialize scenes, events, or items. Still image capturing devices, such as analog and digital cameras, include a lens, a shutter, and some manner of image sensor. In addition, most modern cameras include a processor and/or other control electronics that function to control shutter speed, aperture, flash, focus, etc.
The shutter and the image sensor are the main components of a still image capturing device and operate together in order to produce an image. In operation, the shutter is opened briefly to expose the image sensor to focused light from a lens and thereby form an image. The operation of the shutter is very important, and the quality of the captured image depends on a proper exposure time based on lighting, movement of the subject, focus distance, etc.
A prior art shutter approach used a mechanical shutter. The mechanical shutter has been widely used for a number of years and is generally in the form of an iris-type shutter. However, the prior art mechanical shutter has many drawbacks, including weight, large size, susceptibility to dirt and wear, and the difficulty of precisely controlling shutter exposure times over a wide range of conditions. In addition, the mechanical shutter exposes the entire image as a unit and essentially at once (however, the iris mechanism is open at the center for a longer length of time than at the peripheral region of the iris).
In some prior art cameras, the mechanical shutter is electronically activated by a motor or other electrical actuator. This may produce a more accurate shutter control, but consumes a lot of electrical power, is inflexible, and still exposes the entire image as a unit and for an essentially constant duration.
The prior art therefore cannot control a focus depth of an image in order to capture image portions or objects at different focus depths. For example, in an image of a person in front of a background, prior art image capturing devices focus to the person, and the entire image is captured at that single focus depth. As a result, the background is out of focus. An image captured according to the prior art therefore may have portions that are in focus and may have portions that are out of focus.
Therefore, there remains a need in the art for improvements in still image capturing devices.